US Breast Cancer Cases May Rise 50 Percent by 2030

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PHILADELPHIA — The number of breast cancer cases diagnosed each
year in the United States could rise 50 percent during the next
15 years, a new study suggests.

By 2030, there will be 441,000 new
breast cancers diagnosed yearly in U.S. women ages 30 to 84,
according to the study's estimates. That's up from 283,000 breast
cancer cases in 2011.

Part of the reason for the rise in breast cancer cases is
simply that the population is growing, so there will be more
cases, said study researcher Philip Rosenberg, a senior
investigator in the division of cancer epidemiology and genetics
at the National Cancer Institute (NCI), who presented the
findings here today at the meeting of the American Association
for Cancer Research.

People are also living longer, and cancer risk increases with
age. Finally, different generations of women may also have
differences in lifestyle factors that could affect the risk of
breast cancer — for example, women in today's older generations
may have been less likely to have breastfed their children,
Rosenberg said.

The new estimates include cases of both invasive breast cancer
and "in situ" conditions (which are considered by some to be the
earliest form of breast cancer, but by others to be a
precancerous state). In situ cases are detected almost entirely
through screening, but in the new study, the researchers assumed
that levels of screening would remain about the same as they are
now.

The researchers predict there will be more
breast cancers diagnosed in older women : Breast cancers in
women ages 70 to 84 accounted for 24 percent of all cases in
2011, but will account for 35 percent of cases in 2030. In
contrast, the proportion of breast cancers in women ages 50 to 69
is expected to decrease from 55 percent to 44 percent.

In addition, the proportion of in situ cases that are fueled by
the hormone estrogen (known as ER-positive breast cancer) will
increase — such cases accounted for 19 percent of all in situ
cases in 2011, but that number will be 29 percent in 2030,
according to the study. [ 6
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A silver lining of the findings is that the study estimates there
will be fewer breast tumors that are not
fueled by estrogen, which are among the most
difficult-to-treat types of breast cancer, Rosenberg said. The
proportion of these "ER-negative" breast cancers is expected to
decrease from 17 percent in 2011 to 9 percent in 2030.

The reason for this decrease is not known, but the researchers
speculate that it might be due to an
increase in women breastfeeding their children, and also an
increase in women delaying their first pregnancy. A younger age
at first pregnancy, and not breastfeeding have both been linked
with an increased risk of ER-negative breast cancer, the
researchers said. Knowing more about why ER-negative breast
cancers are declining may provide researchers with clues about
how to prevent this type of breast cancer, Rosenberg said.

To come up with the new estimates, the researchers analyzed data
from the NCI and took into account population projections from
the U.S. Census Bureau. They then used a mathematical model to
make their predications.